Electric switch



Dec. 18, 1934. w. R. WALKER' 1,984,505

ELECTRIC SWITCH v Filed Dec. 13, 1932 Viv/7171710017.?

INVENTOR BY I ATTORNEY UNITED STATES PATENT. OFFICE The present invention Warren 3. Walker,

General Electric Hoboken, N. J., a 0

Short Hills, N. 1., asslgnor t6 Vapor Lamp Company, orporation of New Jersey Application December 13, 1932, Serial No. 647,015

9 Claims.

relates to electric circuit makers and breakers, and in particular to those operating in a vacuum.

A particular 0 vide a magnetically will be reliable in provide a switch of operation.

bject of the invention is to prooperated vacuum switch which Another object is to this type which will be simple and inexpensive, and which will have along useful life. ,Still other invention will 'appe objects and advantages of my ar from the following detailed specification, or from an inspecton of the accom- 'panying drawing.

The invention consists in the novel device hereinafter set forth and claimed 'FOI' many years attempts have been made to produce electric switches in which the circuit is made or broken between solid contacts within an evacuated chambe r, because it was recognized that this type of switch had many advantages. Due to the difiiculties which are obviously inherent in mechanical movement of the contacts within an evacuated chamber these switches were usually designed for ly, however, a

mag

netic operation. Unfortunateserious difiiculty has likewise been encountered in magnetic operation of these switches, as a progressed beyond difiiculty is caused in any ofthese de to freeze together result of which they have never the'experimental stage. This by the fact that the contacts vices have a serious tendency upon closure of the circuit.

Since the magnetic gap is necessarily large in thesedevices,

to separate these small, so that it has and since the armature must have a relatively small mass in order age to the enclosing the latter is of glass,

to prevent damenvelope, particularly where the magnetic force available frozen contacts is relatively been impossible to assure positive opening of the circuit.

I have now discovered that this difllculty can be entirely eliminated by providing a novel switch structureof my invention. According to my invention two fixed nected by a freely appreciable length bridging member-c terial which servesv as an armature.

contacts are electrically conmovable bridging member of At least a portion of this onsists of a magnetizable ma- With this construction'it is obvious that there are two contact points. Experience has shown ing of 'the c other of th taneously. Hence,

that the freeztacts always occurs at one or the points, but not at both simuleven though one end of the bridging member is from the other end thereof is aways free, and the magnetic attraction of this free end produces ment on the frozen an appreclabe turning movecontacts, even in aweak field,

due to the length of the lever moment has been found to be quite adequate to free the contact which is frozen. As a further refinement, however, I prefer to make my bridging member in the form of a tube with a rod of magnetic material freely movable therein. This offers the further advantage that the magnetic rod immediately starts to move upon application of the magnetic field, and thus strikes a hammer blow on the surrounding tube. This blow, coupled with the turning moment, is sufilcient to separate the contacts even in the most aggravated cases of sticking which have been encountered.

For the purpose of illustrating my invention I have shown in the accompanying drawing a preferred form of switch embodying the foregoing features, together with a modification thereof. In the drawing 'Fig. 1 is an elevational view, in part section, of my novel switch,

Fig. 2 is a sectional view taken on the line 2-2 of Fig. 1,

Fig. 3 is an enlarged view, in part section, of the bridging membe Fig. 4 is an end view of said bridging member, and

Fig. 5 is a perspective view of a modification of the fixed contact structure. 7

As shown in Figs. 1 and 2 I preferably form my novel switch with a tubular envelope 1 of any suitable material. A pair of inleads 2 are sealed into opposite ends of this envelope through a conventional seal. These inleads may be of any suitable material, but where a boro-silicate glass is used for the envelope 1 these inleads are conveniently formed of tungsten. A hubbed disc 3 of suitable insulating material, such as porcelain, or the like, is mounted for free rotation on each of said inleads with the hub side against said seal. The diameter of said disc is only slightly less than the inner diameter of the envelope 1. A metal sleeve 4, which in practice is formed as a closely wound helix of nickel wire, is slipped over the end of each of said inleads 2 to a point adjacent'to said discs 3, said sleeves thus serving as retaining means for said discs 3. A transverse metal plate entirely across the interior of the envelope 1 is then placed horizontally on each of the sleeves 4 near the end of the associated inlead 2. These plates. may be made of copper, nickel or the like, but tungsten or molybdenum is preferred therefor, due to the fact that these metals have a better resistance to disintegration by the arcs incidental to operation of any switch. Each plate 5 is welded arm. This turning suitable getter. These parts are, of course, all

assembled on the respective inleads 2 prior to sealing into the envelope 1.

A tubular bridging member 8 rests upon the contact members and is slightly shorter than the distance between the discs 3, while the diameter thereof is appreciably greater than the gap between said discs 3 and the envelope 1. Thus this bridging member has considerable freedom of movement, but cannot escape from its position above the contact plates 5, nor can it become wedged between the discs 3 and the envelope.

Said bridging member may be made of tubing of copper, nickel or the like, if desired, but I prefer to make it of tungsten in orderto increase the useful life of my switch, in which case it is most conveniently formed of tungsten wire of, say, mils. diameter in a closely wound helix, such as shown in the drawing. Due to the rigidity of tungsten this helix behaves substantially the same as a tube. Within said bridging member 8 there is a rod 9 of iron or other magnetic material. Said rod is slightly shorter than said bridging member and has a diameter appreciably less than the interior diameter of the latter, so that it is free to, move therein. Said rod is retained within said bridging member by the end turns thereof, which are bent across the axis of said bridging member, as particularly shown in Fig. 4, although it is obvious that the ends of said bridging member may be plugged in various other way if desired, to produce the same result.

In some cases the fixed contact members may be modified, as shown in Fig. 5, where the back edge of the contact plate 5 is turned up to form a stop for the end of the bridging member 8. In thiscase there is no need, of course, for the discs 3.

After the complete device has been assembled as previously described, the envelope 1 is evacuated to as good a vacuum as possible, the various elements being degassed by the application of heat during this'evacuation. This heat is preferably induced in the variousmetal parts by a high frequency magnetic field, care being employed not to heat the pellet 6 until the evacuation is complete. Said pellet is then heated to a temperature suflicient to volatilize the magnesiumtherein which thereupon condenses upon the walls of the envelope 1. The residual gas is cleaned up by said magnesium, which thus not only produces bu maintains an extremely good vacuum. It is be understood, however, that in some cases it is not necessary to provide such a good vacuum, and that where'desired a gas such as hydrogen or a vapor such as that of mercury, maybe provided in the envelope 1. Said envelope 1 is thensealed off and the switch is complete.

In the operation of the switch shown in Figs. 1-4 the switch envelope 1 is placed below the poles of an electromagnet, the poles 10 thereof being shown conventionally in Fig. 1, said poles each terminating directly above a contact plate 5. Whenever said electromagnet is energized the rod 9 is attracted toward the top of the envelope 1. The first movement of this rod in response to this attraction is independent of the tubular member 8, until the slack has been taken up therebetween. Thus said rod 9 delivers a hammer blow to the member 8 which loosens any frozen or sticking contacts. and thereafter said rod 9 and bridging member 8 move upwardly together, the circuit through the switch being thereupon interrupted. This loosening of the frozen contacts is greatly facilitated, of course, due to the fact that one end of the member 8 is always free to exert a turning moment on the frozen contacts, thus making the hammer blow delivered by the rod 9 at this end especially effective. The circuit remains open, of course, so long as the electromagnet is energized. As soon as it is deenergized, however, the bridging member again falls back onto the contact plates 5, closing the circuit through the switch. Due to the great freedom of movement of the bridging member 8 it may happen, of course, that said member will occasionally tend to assume a sloping position against one of the discs 3, in which position the circuit would, of course, remain open. Said disc 3 is free to rotate, however, under the weight of the bridging member, and hence said bridging member immediately drops to the contact plate 5 and closes the circuit. Thus my novel switch may be absolutely relied upon to positively open and close the circuit therethrough whenever desired. r

When the modified fixed contacts shown in Fig. 5 are used the operation of the switch is virtually the same as previously described. With this construction, however, the circuit is closed as soon as the bridging member 8 makes contact with both of the contact plates 5, regardless of the angle of said bridging member. In some cases, however, the contacts may become frozen when the bridging member is at a considerable slope. While this condition has been overcome by the turning moment and hammer action previously described in all the cases observed, it is believed that the optimum conditions for the positive opening of the circuit irrespective of freezing 'occur when the bridging member is horizontal before the circuit is closed. Hence the structure shown in Figs. 1-4, in which this is assured, is preferred.

The low mass of the moving parts of this novel switch is an extremely desirable feature thereof, since .it greatly reduces the impacts received by the envelope both in shipment and in operation, with a consequent virtual elimination of the breakage hazard. This low mass also makes possible the operation of the switch at high frequency. Another desirable feature of my novel from one side of the bridging member, rather than axially thereof. Hence there is no tendency for said bridging member to bind against a wall of the envelope under the influence of the magnetic field, such as tends to occur when axial movement is relied upon. Another novel feature of my structure results from the freedom of movement of the bridging member 8, which permits it to make contact with the contact plates 5 at a different point every t Furthermore the contact is equally likely to be made to a different point on said bridging member each time, due torotation and longitudinal movement thereof. As a result pitting is virtually eliminated, and my switch has an exceptionally long useful'life.

This novel switch is especially desirable for use where an extremely rapid response is required, and especially where it is desired to abruptly open a circuit. The switch illustrated, for example, is especially designed for use in combination with an inductance which is energized whenever said switch is closed to generate high voltage surges, such as used to start a mercury arc lamp of the Cooper Hewitt type. When so used it is found that this switch cooperates in a unique manner with the associated circuit, due to the nature of the circuit interruption, to produce a high frequency discharge of extremely high voltage which is unusually effective.

While I have described my invention by reference to certain specific structures it is to be understood that it is not limited thereto, it being obvious that various omissions, substitutions and changes, within the scope of the appended claims may be made therein without departing from the spirit of my invention.

I claim as my invention:

1. An electric circuit maker and breaker comprising a sealed envelope, two fixed contacts sealed into said envelope, and a relatively long bridging member extending between said contacts, at least a portion of said member being made of a magnetizable body, said fixed contacts being spaced apart by a distance slightly less than the length of said member, whereby each end of said member engages one of said contacts.

2. An electric circuit maker and breaker comprising an evacuated envelope, two fixed contacts of solid material sealed into said envelope, and a cylindrical bridging member extending between said contacts, at least a portion of said member consisting of a magnetizable body, said fixed contacts being spaced apart by a distance slightly less than the length of said member, whereby each end of said member engages one of said contacts.

3. An electric circuit maker and breaker comprising an evacuated envelope, two fixed contacts sealed into said envelope, a tubular bridging member extending between said contacts, and a magnetizable body within said bridging member and freely movable therein.

4. An electric circuit maker and breaker comprising an evacuated envelope, two fixed contacts sealed into said envelope, a relatively long bridging member extending between said contacts, at least a portion of said member consisting of a magnetizable body, and means to prevent axial displacement of said bridging member, said fixed contacts being spaced apart by a distance slightly less than the length of said member, whereby each end of said member engages one of said contacts.

5. An electric circuit maker and breaker comprising an evacuated envelope, two fixed contacts sealed into said envelope, a bridging member extending between said contacts, at least a portion of said member consisting of a magnetizable body, and means to prevent axial displacement of said bridging member, said means comprising a pair of members which are rotatably supported within said envelope.

6. An electric circuit maker and breaker comprising an evacuated envelope, two fixed contacts sealed into said envelope, and a relatively long resilient bridging member extending between said contacts, each end of said member being adapted to engage one of said of said member consisting of a magnetizable body.

'7. An electric circuit maker and breaker comprising an evacuated envelope, two fixed contacts sealed into said envelope, and a relatively long helically wound wire bridging member consisting in part of magnetizable material extending between said contacts, each end of said member being adapted to engage one of said contacts.

8. An electric circuit maker and breaker comprising an evacuated envelope, two fixed contacts sealed into said envelope, a relatively long bridging member of helically wound wire extending between said contacts, each end of said member being adapted to engage one of said contacts, and

a magnetizable body freely movable within said bridging member.

9. An electric circuit maker and breaker comprising an evacuated envelope, two fixed contacts sealed into said envelope, and a relatively long bridging member extending between said contacts, each end of said bridging member being adapted to engage one of said contacts, at least aportion of said bridging member consisting of a magnetizable body, said bridging member being so disposed with respect to said contacts that it is out of contact therewith whenever it reaches one of its limits of movement.

WARREN R. WALKER.

contacts, at least a portion 

